This pilot study will attempt to establish behavioural criteria by which social facilitation of copulation might be recognized and quantified in monkeys. Breeding in Cercopithecus monkeys seems to be generally timed by climatic changes, copulation occurring during the long dry season. Social facilitation has been implicated in synchronizing conception and so limiting breeding seasons. The possibility that closely related species may show different degrees of synchrony will be explored, following up several lines of circumstantial evidence. Comparisons will be made between wild and captive populations of Cercopithecus mitis experiencing the same climatic changes, between these and the same species living in the wild in a different climate, and between different species living in the same climate, both in the wild and in captivity. The study will be made in Kenya.